This invention relates to a system for forming the joints of concrete slabs used in the construction of roadways, floors and the like.
The basic system of forms including screed and screed stakes is well known and is illustrated, for example, in the Self U.S. Pat. No. 3,561,721 dated Feb. 9, 1981, the Tone U.S. Pat. No. 3,401,612 dated Sept. 17, 1968, the Welch U.S. Pat. No. 3,497,172 dated Feb. 24, 1970 and the Artigalas et al U.S. Pat. No. 3,057,269 dated Oct. 9, 1962. The screed stakes are generally made of metal, approximately 0.07 inches in thickness, approximately 1.00 to 1.25 inches in width and from 12 to 24 inches in length depending on the type of soil in which they are to be driven. Such stakes generally are provided with a central channel for reinforcing purposes with the channel terminating just short of the upper end of the stakes so that the upper end is substantially planar and may be received in a downwardly opening pocket formed on the topside of the screed. Such stakes may also be provided with one or more "fingers" or ear-like members formed out of the stake material to extend upwardly alongside the stake to form an upwardly opening pocket into which the lower side of the screed may be inserted.
The vertical depth of the concrete slabs being poured, and thus the vertical width of the screed necessary to form the key joint in the slab, differs substantially with the four typical dimensions being 3.5, 4.5, 5.5 and 7.5 inches. With known systems, it has been necessary to maintain an inventory of stakes with these ear-like members at different dimensions from the top end of the stake, so that a screed of the desired vertical dimension may be held securely in place. The maintenance of this inventory of stakes is costly not only in the initial cost of procuring the stakes, but in the time and effort necessitated in maintaining their separation, as well as the space needed in the transportation to and storage thereof at the site. There is thus a need for a "universal" stake which may be used with screeds of differing vertical dimensions.
Known attempts to provide a "universal" stake have included the location of a single ear-like member located one on each side of the central reinforcing channel in the stake at two different vertical heights. Such stakes have the disadvantage in that they provide only a single ear-like member for the screed thereby increasing the likelihood of an undesirable rotation between screed and stake and require two different stakes for the four standard slab depths.
It is accordingly an object of the present invention to obviate the deficiencies of the known systems and to provide a system having a single "universal" stake usable with each of the four standard screed depths.
It is a further object of the present invention to provide a system having a single "universal" stake usable both at the ends and intermediate the length of the screed.
The advantages of the present invention are achieved through the use of a stake provided with three vertically spaced pairs of ear-like members located one each on opposite lateral sides of the reinforcing channel in the stake, and by the use of a screed of the fourth vertical width having a plurality of spaced slots located adjacent the top of the key through which the top of the stakes may pass when the fourth screed is used with one of the three sets of fingers.
The advantages of the present system will be readily apparent to one skilled in the art from the claims and from the following detailed description when read in conjunction with the appended drawings.